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A high-resolution paleoecological record provides a 2690 year-long fossil pollen and charcoal history from Lake Ayauchi, Ecuador, in lowland Amazonia. The record begins with a landscape that is already partially deforested and in which maize is being grown. Dated charcoal fragments from local soils coincide with fire events and peaks of land clearance seen in the lake sediment record. After c. AD 550 grass pollen becomes less abundant, as a broad array of forest types show small increases in abundance. Between c. AD 750 and 1280, Zea mays pollen was at its most abundant. Although maize cultivation continued until the AD 1700s, forest pollen abundance showed a significant increase at c. AD 1260. Another transition at c. AD 1420, which saw a transition from dominance by early successional taxa and an increase in mid-successional elements, suggests the onset of reduced human activity at the site. Fossil maize is found in a lower proportion of samples, disappearing altogether for a century in the late 1700s. Forest taxa increase in abundance and charcoal disappears from the record at c. AD 1790. These data suggest a complex social history prior to and following European arrival with phases of forest clearing and episodes of apparent regrowth at c. AD 500, 950, and 1260. Increased forest pollen after c. AD 1260 and a reduction in maize pollen abundance suggests some abandonment, with a second, relatively late, depopulation following European Conquest (c. AD 1790). Evidence is not found supporting reforestation associated with European arrival.

Biodiversity contributes to the ecological and climatic stability of the Amazon Basin1,2, but is increasingly threatened by deforestation and fire3,4. Here we quantify these impacts over the past two decades using remote-sensing estimates of fire and deforestation and comprehensive range estimates of 11,514 plant species and 3,079 vertebrate species in the Amazon. Deforestation has led to large amounts of habitat loss, and fires further exacerbate this already substantial impact on Amazonian biodiversity. Since 2001, 103,079–189,755 km2 of Amazon rainforest has been impacted by fires, potentially impacting the ranges of 77.3–85.2% of species that are listed as threatened in this region5. The impacts of fire on the ranges of species in Amazonia could be as high as 64%, and greater impacts are typically associated with species that have restricted ranges. We find close associations between forest policy, fire-impacted forest area and their potential impacts on biodiversity. In Brazil, forest policies that were initiated in the mid-2000s corresponded to reduced rates of burning. However, relaxed enforcement of these policies in 2019 has seemingly begun to reverse this trend: approximately 4,253–10,343 km2 of forest has been impacted by fire, leading to some of the most severe potential impacts on biodiversity since 2009. These results highlight the critical role of policy enforcement in the preservation of biodiversity in the Amazon. Remote-sensing estimates of fires and the estimated geographic ranges of thousands of plant and vertebrate species in the Amazon Basin reveal that fires have impacted the ranges of 77–85% of threatened species over the past two decades.

*Center for Applied Biodiversity Science, Conservation International, Washington, D.C, 20037, U.S.A.†Climate Change Research Group, Ecology and Conservation, National Botanical Institute, Cape Town, South Africa‡The World Bank, Washington, D.C. 20433, U.S.A.§Botany Department, University of Cape Town, Cape Town, South Africa**Department of Biological Sciences, College of Science and Liberal Arts, Florida Institute of Technology, Melbourne,FL 32901–6975, U.S.A.††Environment Department, University of York, York, Y010 5DD, United Kingdom‡‡Adaptation and Impacts Research Group, Environment Canada at the Faculty of Environmental Studies, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada§§Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom

Oceanic islands support unique biotas but often lack ecological redundancy, so that the removal of a species can have a large effect on the ecosystem. The larger islands of the Galápagos Archipelago once had one or two species of giant tortoise that were the dominant herbivore. Using paleoecological techniques, we investigate the ecological cascade on highland ecosystems that resulted from whalers removing many thousands of tortoises from the lowlands. We hypothesize that the seasonal migration of a now-extinct tortoise species to the highlands was curtailed by decreased intraspecific competition. We find the trajectory of plant community dynamics changed within a decade of the first whaling vessels visiting the islands. Novel communities established, with a previously uncommon shrub, Miconia, replacing other shrubs of the genera Alternanthera and Acalypha. It was, however, the introduction of cattle and horses that caused the local extirpation of plant species, with the most extreme impacts being evident after c. 1930. This modified ecology is considered the natural state of the islands and has shaped subsequent conservation policy and practice. Restoration of El Junco Crater should emphasize exclusion of livestock, rewilding with tortoises, and expanding the ongoing plantings of Miconia to also include Acalypha and Alternanthera.

Much has yet to be learned of the spatial patterning of pre-Columbian people across the Tropical Andes. Using compiled archaeological data and a suite of environmental variables, we generate an ensemble species distribution model (SDM) that incorporates general additive models, random forest models and Maxent models to reconstruct spatial patterns of pre-Columbian people that inhabited the Tropical Andes east of the continental divide, within the modern countries of Bolivia, Peru and Ecuador. Within this region, here referred to as the eastern Andean flank, elevation, mean annual cloud frequency, distance to rivers and precipitation of the driest quarter are the environmental variables most closely related to human occupancy. Our model indicates that 11.04% of our study area (65 368 km 2 ) was likely occupied by pre-Columbian people. Our model shows that 30 of 351 forest inventory plots, which are used to generate ecological understanding of Andean ecosystems, were likely occupied in the pre-Columbian period. In previously occupied sites, successional trajectories may still be shaping forest dynamics, and those forests may still be recovering from the ecological legacy of pre-Columbian impacts. Our ensemble SDM links palaeo- and neo-ecology and can also be used to guide both future archaeological and ecological studies. This article is part of the theme issue ‘Tropical forests in the deep human past’.

A 370,000-year paleoecological history of fire spanning four glacial cycles provides evidence of plant migration in response to Andean climate change. Charcoal, an indicator of fire, is only occasionally observed in this record, whereas it is ubiquitous in Holocene-aged Andean records. Fire is a transformative agent in Amazonian and Andean vegetation but is shown to be rare in nature. As humans promote fire, fire-free areas become microrefugia for fire-sensitive species. A distinction is drawn between microrefugia resulting from fire-free zones and those caused by unusual climatic conditions. The importance of this distinction lies in the lack of warmer-than-modern microrefugia aiding upslope migration in response to warming, whereas fire-free microrefugia support tree species above modern tree line or in areas of Amazonia least used by humans. The synergy between fire, deforestation, and climate change could promote a state-change in the ecosystem, one where new microrefugia would be needed to maintain biodiversity. Past tipping points are identified to have occurred within ca. 1°C–1.5°C of modern conditions. The recent climatic instability in both Amazonia and the Andes is viewed in the context of ecological flickering, while the drought-induced and fire-induced tree mortality are aspects of critical slowing down; both possibly portending an imminent tipping point.

Humid montane forests are challenging environments for human habitation. We used high-resolution fossil pollen, charcoal, diatom and sediment chemistry data from the iconic archaeological setting of Laguna de los Condores, Peru to reconstruct changing land uses and climates in a forested Andean valley. Forest clearance and maize cultivation were initiated during periods of drought, with periods of forest recovery occurring during wetter conditions. Between ad 800 and 1000 forest regrowth was evident, but this trend was reversed between ad 1000 and 1200 as drier conditions coincided with renewed land clearance, the establishment of a permanent village and the use of cliffs overlooking the lake as a burial site. By ad 1230 forests had regrown in the valley and maize cultivation was greatly reduced. An elevational transect investigating regional patterns showed a parallel, but earlier, history of reduced maize cultivation and forest regeneration at mid-elevation. However, a lowland site showed continuous maize agriculture until European conquest but very little subsequent change in forest cover. Divergent, climate-sensitive landscape histories do not support categorical assessments that forest regrowth and peak carbon sequestration coincided with European arrival. Multi-proxy palaeoecological methods reconstruct phases of land clearance, maize cultivation and forest regrowth in the High Andes centuries before European incursion, and do not support the idea that forest regrowth and peak carbon sequestration were coincident with European arrival.

Mid-elevation Andean ecosystems have immense species richness and endemism. Taxonomic composition is known to change through time on the eastern slopes of the Andes as a result of climatic change and disturbance events, both natural and by human actions. Fossil phytoliths can capture local scale vegetation changes, especially among monocotyledonous plants. Phytolith production is high in grasses and palms, plant groups that are particularly sensitive to climatic changes and disturbance events in Andean ecosystems. Here, we reconstruct four centuries of local-scale vegetation change and the corresponding fire history from lake sediment records retrieved from Lagunas Cormorán and Chimerella, located at ca. 1,700 m a.s.l. in the mid-elevation Andean forests of eastern Ecuador. The charcoal analysis of the lake sediments showed no sign of past fires, and no evidence of cultivation was found at either lake. The phytolith assemblages indicated changes in the relative abundances of palms, grasses and trees over the last few centuries, suggesting that mid-elevation Andean phytolith assemblages are sensitive to local scale vegetation dynamics. The largest change in vegetation occurred at the end of the Little Ice Age, at which point the diversity of palm phytoliths decreases. These phytolith assemblages are probably responding to changes in the cloud base position through time, which strongly influences the distributions of many plants and animals.

A 42,000-year record of coprophilous fungal (Sporormiella, Podospora, Cercophora), fossil pollen and charcoal data assessed megafaunal use of woodland versus grassland settings in Central American landscapes by Pleistocene megafauna. The sedimentary record from Lake Petén-Itzá showed that vegetation growing around the lake shifted between scrub grasslands, Pinus-dominated woodlands, Quercus-dominated woodlands, and tropical seasonal forest. A series of regression analyses and probabilistic models revealed that vegetation assemblages and temperature influenced the abundance of coprophilous fungus, a proxy for megafaunal abundance. We found that megafaunal populations were almost continuously present around Petén-Itzá during the Pleistocene, and that the peak abundances appear to have been associated with cool, moist Quercus-rich parklands. In contrast, the lowest inputs of coprophilous fungi occurred during cold, dry events when scrub grasslands expanded. The dry grasslands may have been nutrient-limited, offering poor quality grazing for megafauna. The decline of the Pleistocene megafauna at Petén-Itzá was a multi-stage event, with a series of population collapses prior to an inferred local extirpation c. 13,600 years ago.

The Little Ice Age (LIA - A.D. 1400 to 1820, 550 to 130 cal yr BP) was a significant worldwide climatic fluctuation, yet little is known about its impact on the ecology of Amazonia or its human inhabitants. Using organic geochemistry and diatoms, we investigate the limnological impact of this event in an Amazonian record spanning the last 760 years. The sedimentary record is from Lake Pata (Lagoa da Pata), which lies on the Hill of Six Lakes (Morro dos Seis Lagos), in the wettest section of the western Brazilian Amazonia. We found that many of the diatom taxa recovered from this remote site are either morphotypes of known species or species new to science. Eunotia and Frustulia dominated our fossil diatom assemblage over time, indicating oligotrophic waters of low pH. The limnological characteristics of this pristine system changed very little over the last millennium, except for a slight intensification of precipitation indicated by the increase in Aulacoseira granulata abundances, in C/N ratios, and in sedimentation rates. This phase lasted from 1190 to 1400 A.D. (760 to 550 cal yr BP). Although occurring before the onset of LIA, the observed change matched increases in precipitation observed in Venezuelan glaciers and Peruvian speleothems. We conclude that although the changes in precipitation detected in our lake match the timing of precipitation increase in some South American records, the event was shorter and its effects in this region of Amazonia were mild compared with other regional records. Our paleolimnological data provide additional insights into the interpretation of a remarkably stable fossil pollen record, in that the highest variance in vegetation occurred over the last millennium. Because Lake Pata has no human influence, part of its value is in providing a reference, with which variability in other settings that do have a human history, can be compared.

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A current goal among many scientific disciplines is to incorporate data on past human land use and climate change into current global climate and vegetation models. Here, we used existing archaeological and paleoecological data to provide a spatiotemporal reconstruction of human history in Greater Amazonia over the Holocene. We used an ensemble distribution model based on a database of georeferenced14C-dated material and environmental factors to predict the changes in spatial distributions of past human occupation sites. We ran these models for the precultivation (13,000–6000 yr ago), early cultivation (6000–2500 yr ago), and late cultivation (2500–500 yr ago) periods. The ensemble models suggest that people mostly inhabited the peripheral areas of Greater Amazonia and the eastern sections of the main Amazon River and its larger tributaries during the precultivation period. Human populations began growing exponentially through the early cultivation period, and people spread and expanded into the interior forests and along river channels in western Amazonia. Populations continued growing through the late cultivation period in these same regions. Our results suggest that many forests, particularly in the peripheral regions and riverine locations, may still be in recovery from disturbances that have occurred repeatedly through the Holocene.

A new fossil pollen, Sporormiella, and sediment chemistry record from Lake Llaviucu, Ecuador, spanning the period from 16,280–9000 years Before Present, provides a high-resolution record of paleoecological change in the high Andes. The deglacial transition from super-páramo through páramo grasslands, to Andean forest is traced, with near-modern systems being established by c. 11,900 years ago. It is suggested that forest elements probably existed in microrefugial populations close to the ice front. Sporormiella is used as a proxy for megafaunal abundance, and its decline to background levels is inferred to indicate a local extinction event at c. 12,800 years ago. About 1800 years prior to the extinction, charcoal becomes a regular sedimentary component in this very wet valley. An early date for human activity in the valley is suggested, with the direct implication of humans in the extinction of the megafauna.

Tropical forests are shifting in species and trait composition, but the main underlying causes remain unclear because of the short temporal scales of most studies. Here, we develop a novel approach by linking functional trait data with 7000 years of forest dynamics from a fossil pollen record of Lake Sauce in the Peruvian Amazon. We evaluate how climate and human disturbances affect community trait composition. We found weak relationships between environmental conditions and traits at the taxon level, but strong effects for community‐mean traits. Overall, community‐mean traits were more responsive to human disturbances than to climate change; human‐induced erosion increased the dominance of dense‐wooded, non‐zoochorous species with compound leaves, and human‐induced fire increased the dominance of tall, zoochorous taxa with large seeds and simple leaves. This information can help to enhance our understanding of forest responses to past environmental changes, and improve predictions of future changes in tropical forest composition.

This study hindcast the geographic distribution of 18 Indo-Pacific scleractinian coral species, with different sensitivities to modern heat stress, into the last glacial maximum (LGM), some 18,000 years ago, when sea-surface temperatures were 2–4oC cooler and sea level was ~130 m lower than on contemporary reefs. Identifying geographic provinces from the past may provide clues into genetic affiliations through time and provide some insight into how some coral species might respond to contemporary climate change. Coral habitat in the Indo-Pacific was reduced by 70% in the LGM. We identified five Indo-Pacific biogeographical provinces for corals during the LGM — (i) the western Indian Ocean, (ii) Southeast Asia, (iii) Indonesia and northwestern Australia, (iv) northeastern Australia and the Pacific Islands, and (v) the eastern Pacific. These provinces align with provinces recently identified using genetic markers. Given that the Quaternary was dominated by glacial conditions, the distributional legacies left through glacial dominance over that 2.6 million-year period may have also left evolutionary legacies. These glacial legacies may explain why contemporary corals live close to their upper thermal thresholds, which in turn have major consequences as we move into unprecedented rates of ocean warming.

Understanding the biogeography of past and present fire events is particularly important in tropical forest ecosystems, where fire rarely occurs in the absence of human ignition. Open science databases have facilitated comprehensive and synthetic analyses of past fire activity, but charcoal datasets must be standardized (scaled) because of variations in measurement strategy, sediment type, and catchment size. Here, we: i) assess how commonly used metrics of charcoal scaling perform on datasets from tropical forests; ii) introduce a new method called proportional relative scaling, which down-weights rare and infrequent fire; and iii) compare the approaches using charcoal data from four lakes in the Peruvian Amazon. We found that Z-score transformation and relative scaling (existing methods) distorted the structure of the charcoal peaks within the record, inflating the variation in small-scale peaks and minimizing the effect of large peaks. Proportional relative scaling maintained the structure of the original non-scaled data and contained zero values for the absence of fire. Proportional relative scaling provides an alternative scaling approach when the absence of fire is central to the aims of the research or when charcoal is infrequent and occurs in low abundances.

M.B.B would like to acknowledge funding from the National Science Foundation (grant nos. EAR1338694 and BCS0926973), the Belmont Forum, and the National Aeronautics and Space Administration (grant no. NNX14AD31G). C.N.H.M would like to acknowledge funding from the European Research Council (ERC 2019 StG 853394). C.N.H.M and M.F.R would like to acknowledge funding from the Netherlands Organisation for Scientific Research (ALWOP.322). S.N.H, M.P, and Jo.V performed this research as a part of the BSc research program of the Institute for Biodiversity and Ecosystem Dynamics at the University of Amsterdam. 1. Modifications of Amazonian forests by pre‐Columbian peoples are thought to have left ecological legacies that have persisted to the modern day. Most Amazonian palaeoecological records do not, however, provide the required temporal resolution to document the nuanced changes of pre‐Columbian disturbance or post‐disturbance succession and recovery, making it difficult to detect any direct, or indirect, ecological legacies on tree species. 2. Here, we investigate the fossil pollen, phytolith and charcoal history of Lake Kumpaka, Ecuador, during the last 2,415 years in c. 3–50 year time intervals to assess ecological legacies resulting from pre‐Columbian forest modification, disturbance, cultivation and fire usage. 3. Two cycles of pre‐Columbian cultivation (one including slash‐and‐burn cultivation, the other including slash‐and‐mulch cultivation) were documented in the record around 2150–1430 cal. year BP and 1250–680 cal. year BP, with following post‐disturbance succession dynamics. Modern disturbance was documented after c. 10 cal. year BP. The modern disturbance produced a plant composition unlike those of the two past disturbances, as fire frequencies reached their peak in the 2,415‐year record. The disturbance periods varied in intensity and duration, while the overturn of taxa following a disturbance lasted for hundreds of years. The recovery periods following pre‐Columbian disturbance shared some similar patterns of early succession, but the longer‐term recovery patterns differed. 4. Synthesis. The trajectories of change after a cessation of cultivation can be anticipated to differ depending on the intensity, scale, duration and manner of the past disturbance. In the Kumpaka record, no evidence of persistent enrichment or depletion of intentionally altered taxa (i.e. direct legacy effects) was found but indirect legacy effects, however, were documented and have persisted to the modern day. These findings highlight the strengths of using empirical data to reconstruct past change rather than relying solely on modern plant populations to infer past human management and ecological legacies, and challenge some of the current hypotheses involving the persistence of pre‐Columbian legacies on modern plant populations. Publisher PDF

Aims: Terrestrial ecosystems are changing in biodiversity, species composition and functional trait composition. To understand the underlying causes of these changes and predict the long-term resilience of the ecosystem to withstand future disturbances, we can evaluate changes in diversity and composition from fossil pollen records. Although diversity can be well estimated from pollen in temperate ecosystems, this is less clear for the hyperdiverse tropics. Moreover, it remains unknown whether functional composition of plant assemblages can be accurately predicted from pollen assemblage composition. Here, we evaluate how community-weighted mean (CWM) traits and diversity indices change along elevation.Location: Amazon–Andes elevation gradient in Peru.Methods: We used 82 modern pollen samples and 59 vegetation plots along the elevation gradient, and calculated CWM traits and diversity indices for each pollen sample and vegetation plot. We also quantified the degree to which taxa are over- or underrepresented by their pollen, by dividing the relative pollen abundance by the relative basal area abundance in the nearby vegetation survey plots (i.e. the R-rel values).Results: We found that CWM wood density increased, and CWM adult height and leaf area decreased with elevation. This change was well predicted by pollen assemblages, indicating that CWM trait–environment relationships based on pollen abundance data provide meaningful results. Diversity (richness, Shannon and Simpson) decreased with elevation for vegetation plots, but these trends could not be observed from pollen assemblages.Conclusions: Our results demonstrate that more research is needed to develop methods that lead to accurate diversity estimates from pollen data in these tropical ecosystems, but that CWM traits can be calculated from pollen data to assess spatial shifts in functional composition. This opens opportunities to calculate CWM traits from fossil pollen data sets in the tropics, with broad implications for improving our understanding and predictions of forest dynamics, functioning and resilience through time.

Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last ~50 ka from Lake Junín (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru’s second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America., How the abrupt warming events recorded in Greenland ice cores during the last glacial cycle have influenced the tropical climate is not well known. Here the authors present new lake sediment data from the Peruvian Andes that shows that these events resulted in rapid glacier retreat and large reductions in lake level.

AimTo investigate cerrado responses to glacial–interglacial climate change and the potential for connective rain forest corridors between the Atlantic Coastal Forest and Amazonian rain forest.LocationThe crater lake of Serra Negra (18 °S, 46 °W) in Minas Gerais, Brazil.Taxon117 fossil pollen types, 22 non‐pollen palynomorphs were documented.MethodsWe recovered 7.82 m of sediment from the lake, and analysed fossil pollen at 62 depth intervals throughout the core. We derived a chronology based on radiocarbon dating with simple rate extrapolation to the base of the core.ResultsThe c. 90,000‐year fossil record showed a trend towards cooler climates at the Last Glacial Maximum (LGM), but interstadial warming coupled with reduced evaporative stress allowed the expansion of woodlands under cool, moist conditions. Cool‐adapted trees were most abundant between c. 67,000 and 48,000 years ago. A cool cerrado‐like environment marked full glacial conditions between c. 48,000 and 34,000 years ago. The peak of the LGM between c. 34,000 and 17,000 years ago is inferred to have been dry as no sediment accumulated in the system.Main conclusionsExpanded ranges of cold‐tolerant forest taxa led to establishment of a series of assemblages without modern analogue. A system characteristic of modern cerrado was rare in the history of this site. Multiple forest expansions were observed, each differing in composition. The periods of forest abundance at Serra Negra were not temporally aligned with forest expansion in the Atlantic Coastal Forest, and did not provide a continuous corridor of similar forest that connected the cerrado to the Atlantic Coastal Forest.

The origin of modern disjunct plant distributions in the Brazilian Highlands with strong floristic affinities to distant montane rainforests of isolated mountaintops in the northeast and northern Amazonia and the Guyana Shield remains unknown. We tested the hypothesis that these unexplained biogeographical patterns reflect former ecosystem rearrangements sustained by widespread plant migrations possibly due to climatic patterns that are very dissimilar from present-day conditions. To address this issue, we mapped the presence of the montane arboreal taxa Araucaria, Podocarpus, Drimys, Hedyosmum, Ilex, Myrsine, Symplocos, and Weinmannia, and cool-adapted plants in the families Myrtaceae, Ericaceae, and Arecaceae (palms) in 29 palynological records during Heinrich Stadial 1 Event, encompassing a latitudinal range of 30°S to 0°S. In addition, Principal Component Analysis and Species Distribution Modelling were used to represent past and modern habitat suitability for Podocarpus and Araucaria. The data reveals two long-distance patterns of plant migration connecting south/southeast to northeastern Brazil and Amazonia with a third short route extending from one of them. Their paleofloristic compositions suggest a climatic scenario of abundant rainfall and relative lower continental surface temperatures, possibly intensified by the effects of polar air incursions forming cold fronts into the Brazilian Highlands. Although these taxa are sensitive to changes in temperature, the combined pollen and speleothems proxy data indicate that this montane rainforest expansion during Heinrich Stadial 1 Event was triggered mainly by a less seasonal rainfall regime from the subtropics to the equatorial region., This work was funded by FAPESP research grant 2015/50683-2 to P.E. De Oliveira, VULPES Project, Belmount Forum.

AimTo determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns of Polylepis woodlands in the Andes.LocationTropical Andes above 2,900 m between 2°S and 18°S of latitude.MethodsPollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution of Polylepis woodlands.ResultsWoodland expansion and fire were correlated with precipitation changes and glacier dynamics from c. 20 to 6 kcal BP (thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcal BP were less common than from 12 kcal BP to modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcal BP, as woodlands recovered from 10.5 to 9.5 kcal BP (about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcal BP were commonplace post‐9.5 kcal BP but did not trigger an equivalent woodland contraction. An increase in the coefficient of variation after c. 5.5 kcal BP suggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years, Polylepis became hyper‐fragmented with over half of sites losing Polylepis from the record and with coefficients of variation paralleling those of glacial times.Main conclusionsPolylepis woodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the last c. 1,000 years.

The last interglacial was the most recent time when temperatures were 1–2 °C above modern, but little is known of this period in the lowland Neotropics. Equally, data for the full glacial period are very limited. A detailed analysis of the period between ~ 137 and 100 ka was completed to provide a paleoecological history of the last interglacial in central Panama. Two additional fossil diatom records from the same depositional basin provided records of the glacial period. Diatom assemblages were compared across all cores and the dominant species of both glacial and interglacial periods was almost always Aulacoseira granulata. Other species, e.g. Aulacoseira agassizii, Achnanthidium minutissimum, Nitzschia amphibia, and Navicula radiosa, had distinctive patterns of abundance within the record, indicating a shallowing of the lake in the last millennia of MIS5e. The period between 119 and 108 ka witnessed the most change within the high-resolution portion of the record suggesting an increased lake level, with expanding lake margins. Other sediment cores collected within the caldera revealed the continued presence of a lake at El Valle through much of the glacial period, with shallowing evident at the time of the LGM. The changes in diatom assemblages at El Valle provide one of the oldest precipitation records from Central America tracking mean ITCZ position between the last interglacial and glacial periods. Furthermore, the evidence for both a wet interglacial and glacial period support palynological findings that the humid environments of Central Panama were not interrupted by glacial aridity.

A paleoecological record from Lake Palotoa (1370 m elevation) in the Andean foothills of Peru spans the last 3800 years. Lake Palotoa lies near the modern cloud base in a location sensitive to changes in atmospheric moisture. In many areas, these forests have been destroyed, but Lake Palotoa shows no sign of human occupation today or in the past. The modern forest surrounding the lake is dominated by the Andean palm, Dictyocaryum lamarckianum, which is also the most abundant taxon in the fossil pollen record. Fossil pollen data show the vegetation assemblages have not experienced strong compositional changes in the late Holocene. Global-scale climatic events such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are identified within the record, though the vegetation responses are subtle. Hedyosmum and Sloanea pollen percentages increase near the onset of the MCA and may reflect decreased seasonality. The LIA coincides with increased Hedyosmum pollen percentages, and increases in Clethra and Begonia, two elements that tend to occupy forests now found at higher elevations. Our findings demonstrate the stability of montane forest systems to natural Holocene climate change.

Whether humans or climate change caused the extinction of megafaunal populations is actively debated. Caves in the Lagoa Santa provide mixed assemblages of megafauna and human remains; however, it remains uncertain the extent to which humans and megafauna interacted or overlapped temporally. Here we present the first paleoecological record from lowland South America that tracks the decline of megafauna and its ecological implications. We provide a data set for pollen, charcoal, and Sporormiella, from two lakes in southeastern Brazil that span the last 23,000 yr. The data showed reduced abundances of Sporormiella and an inferred megafaunal population decline that began 18,000 yr ago, with the functional extinction occurring between 12,000 and 11,500 yr ago. Population declines coincided with wet events. The age of the final megafaunal decline is within the range of the first human occupation of the region. Our data are consistent with climate causing the population collapse, with humans preventing population recovery and inducing extinction. We did not observe some of the ecological repercussions documented at other sites and attributed to the megafaunal extinction. Habitat-specific ecological consequences of the extinction add to the heterogeneity of late Pleistocene and early Holocene landscapes.

National Science Foundation (NSF) RAPID, Program [AGS-1256970, AGS-1561121]; NOAA Climate Program Office; University of Arizona Department of Geosciences; Philanthropic Education Organization; National Science Foundation (NSF) P2C2, Program [AGS-1256970, AGS-1561121]; National Science Foundation (NSF) Geospace Sciences Paleoclimate Program [AGS-1256970, AGS-1561121]

This paper addresses a topic highlighted in recent arguments by Amazonian scholars: the extent to which forms of forest management in prehistory influenced the past and present composition of terra firme and riverine forests. New information on palm phytolith characteristics enabled phytolith analysis on soils sampled from underneath forests in western and central Amazon. We evaluated whether three major economic palms, Oenocarpus bataua, O. bacaba, and Euterpe precatoria, thought to have been significantly enriched by human activities, demonstrated such enrichment. All three palms are hyperdominant species today. We also examined expanded modern phytolith reference collections in a possible context of human management of other arboreal species that involved changes in overall forest structure and diversity during the past several thousand years. Results indicate little to no enrichment of the palms and largely stable forest structure and diversity in terra firme forests through time. Although much research remains, results of this study indicate that prehistoric human modification of Amazonian forest and creation of species hyperdominance was less influential than currently proposed by some Amazonian scholars. Findings contribute toward resolving questions concerning the temporal and spatial scale and characteristics of pre-Columbian human impacts across Amazonia. They also suggest cross-disciplinary insights surrounding the proposed new geological epoch of the Anthropocene.

The Last Interglacial (c. 128,000 to 115,000 years ago) was the last time when global temperatures may have been higher than those of the Holocene, but little is known about vegetation change or paleoclimate during that period in Central America. A new fossil pollen record from the lowland setting of El Valle, Panama, spanned the period from 137,000 to 98,000 years ago. We used multivariate analysis of modern and fossil pollen samples to provide the first regional quantification of Last Interglacial temperature and precipitation change and found mean annual temperatures were c. 1–2 °C warmer than modern, while precipitation was mostly similar to modern. The montane genus Quercus was intermittently present throughout the interglacial period, leading to the inference that this dispersal-limited taxon was surviving in microrefugia. Both charcoal and the early successional genus Cecropia were noticeably rare in the last interglacial compared with the Holocene. The modern absence of Quercus from Central Panama does not appear to be the product of interglacial warming, but rather a result of dry conditions in the late Holocene and human activity. It is suggested that humans greatly increased fire frequency, thereby favoring Cecropia and eliminating Quercus from the lower portion of its elevational range.